1. Field of the Invention
The present invention relates to a straddle-type vehicle having a secondary air supply device arranged to supply secondary air to an exhaust passage of an engine.
2. Description of the Related Art
In some cases, a secondary air supply device which supplies secondary air to an exhaust passage of an engine is provided in a straddle-type vehicle. With the secondary air supply device, a one-way valve (a reed valve) is disposed at a secondary air supply pipe which is communicated with the exhaust passage. The secondary air is supplied to the exhaust passage by utilizing pulsation of exhaust pressure.
In Japanese Unexamined Patent Application No. 2006-183513, a secondary air supply device having a plurality of secondary air supply pipes is disclosed with the aim of increasing the supply amount of the secondary air. In the secondary air supply device, one-way valves disposed at each secondary air supply pipe are arranged to be aligned in the vehicle front-back direction.
However, in the case where a plurality of one-way valves are arranged to be aligned in the vehicle front-back direction as in Japanese Unexamined Patent Application No. 2006-183513, it becomes hard for the secondary air supply pipe to which the one-way valve of the rear side is attached to receive flowing air during traveling of the vehicle. Accordingly, the secondary air in the secondary air supply pipe is expanded due to heat from the engine side. Therefore, there is a problem that a substantial increase in the supply amount of the secondary air is difficult.